Quantum close-coupling calculations of collisional redistribution of light for Ba(1P←1S) perturbed by helium

Cross-sections for optical collisions of the barium atom with He are calculated for a range of detunings around the atomic resonance. Results are obtained from fully quantum mechanical coupled-channels calculations including the ground and two excited molecular (1)Sigma and (1)Pi states. Close-coupling calculations are carried out using the theoretical potential curves for Ba-He, obtained by means of a pseudopotential;SCF-CI technique (Czuchaj, E., Rebentrost, F., Stoll, H., and Preuss, H., 1995, Chem. Phys., 196, 37). For accurate comparison with the experiment (Ni, S. Y., Goetz, W., Meijer, H. A. J., and Andersen, N., 1996, Z. Phys. D, 38, 303), the calculated absorption profile and polarizations have been thermally averaged over the collision energy. The theoretical absorption coefficient and linear polarization ratio agree quite well with the experimental data.